[BUG] project license mutability

[MontrealSergiy]

1. Why project licenses become mutable by creator? I might be wrong but I think in an early version the user project was inaccessible to the user. User might sign one text but then project maintainer changes the texts. Which is a bit unexpected. I think license should be immutable, maybe create special project and data provider for them? User still can delete old and create new version. Some sneaky companies offer agreements that are subject to change without the warning, but at the least they warn users in the original agreement.

2. Deleting licenses without trace is not ideal, no way to check what users agreed in past. Could some copy stay for reference?

3. Also maybe restrict access to files in licensed projects accordingly? (last 2 points may be moved to a separate issue)